The Who, What, Where, When and Sometimes, Why.

Breast Cancer Risk Factors: Birthweight

Studies show women with a higher birthweight (a woman’s weight when she was born) have an increased risk of breast cancer, especially before menopause, compared to women with a lower birthweight [55-61].

A higher birthweight doesn’t appear to be linked to higher estrogen levels in adulthood [62-64]. However, birthweight may be a marker of factors related to growth that are linked to breast cancer risk, such as adult height [63,65-66].

Other reasons behind the link between birthweight and breast cancer risk are under study.

Learn about other early life exposures and breast cancer risk

For a summary of research studies on birthweight and breast cancer risk, visit the Breast Cancer Research Studies section.

Learn about other factors linked to the risk of breast cancer.

Updated 04/22/24